Muffler



Patented Feb. la 1937 Uiwrlau STATES.

amasis I Beecher B. Cary Mpman and Charles Hollerlth, Jackson,

Mich., assignors to Hayes Industries, Inc., Jackson, Mich.,

a corporation of Michigan Application January 13, 1936, Serial No. 58,799

10 Claims.

The present invention relates to silencers and muiilers and more particularly to mufllers used in connection with internal combustion engines -for attenuating the sound of the exhaust.

While several of the features of the invention are independent of the type of gas dow through the muffler, as an important feature resides in improvements in retroverted passage type of mufilers, all the features are illustrated in connection with triple pass constructions.

An object of the invention is to provide a compact, retroverted flow, low back pressure muffier in which the changes in the direction of flow of gas at opposite ends of the muiller is accomplished with the creation of a minimum back pressure by angular conduits as distinguished from the usual practice of direction of the gas at opposite ends of the muilier into expansion chambers. i Y

Another object resides in the improvement in resonator chamber arrangement and construction for acoustic wave attenuation.

Further objects and advantages residing in the specific construction of the conduit louvers, bafiles, and other structural parts of the muffler will become apparent from a consideration of the following detailed description and accompanying drawings wherein,

Fig. 1 is a cross-sectional view taken along the longitudinal axis of the muiller,

Fig. 2 is an enlarged fragmentary plan and view of the louver construction in the gas conduit,

Fig. 3 is a cross-sectional view taken on line III- III of Fig. 2,

. Fig. 4 is a cross-sectional view taken on line IV-IV ofFig. 3,

Fig. 5 is an end view of the muiiler shown in Fig. 1 taken from the left end,

Fig. 6 is a view similar to Fig. 5 of a modified arrangement of the multiple longitudinal extending gas conduits,` and Fig. 7 is a cross-sectional view through the gas conduit showing the construction of a baille and the method employed for securing the same upon the conduit.

Referring to 'the drawings, it will appear ythat the illustrated mulller in Fig. 1 comprises an outer oval shaped imperforate casing I0 having headers I2 and I4 at opposite ends. Inlet and outlet conduits IB and I8 opening through the headers I2 and I4 and connected with straight through gas conduit sections and 22 supported by ybaffles 24 and 26 spaced inwardly from `the headers I2 and I4 to provide resonator chambers 28 and 3U.

Spaced along the conduit sections 20 and 22 are bames 82 supporting the tubes 84 and 35 to jointly define acoustic wave filter chambers 86. Each louver 38 in the conduits 20 and 22 opening into the chamber 36 preferably is formed by piercing the sections 20 and 22 along short parallel lines 40 and 42 and deilecting the central portion 44 outwardly to deilne an arch with openings at 46 and 48 between the curvilinear anchored ends of the portion 44 merging at 50 and 52 with the general contour of theconduit. To prevent closing of the openings 46 and 48 by inwardly deilecting the arch during' Ihandling' and to strengthen the conduit a reinforcing and stiften- `ing rib 54 is provided in the central portion 44. Such louver construction does not appreciably weaken the conduit as no metal is removed.

Moreover, and of more importance, louver construction as illustrated does not create objectionlable high frequency sounds upon passage of the `exhaust gases along the conduit as is oftentimes experienced with conventional perforations. This characteristic perhaps may be attributed to the tangential location of the openings 46 and 48 disposed transvrsely of the direction of the gas flow and to the curvilinear structure of the portions 50 and 52 of the arch 44 which eliminate the presentationof any rough and sharp edges or abrupt shoulders over which the rapidly traveling exhaust gases flow. We have also observed the fact that our louver construction possesses acoustic wave attenuating characteristics which may .be varied by regulating the height of the arch 44. Under some conditions the attenuating characteristic is increased by lowering the arch. As

this accordingly reduces the openings between the arch and the conduit wall a large number of closely positioned louvers may be required which is possible without objectionable reduction in the strength of the conduit with our'louver construction. I

` 'I'he return conduit section 56 is supported in the bailies 24 and 26 in the manner of the conduit sections 20 and 22. Embracing the section 56 is a tube 58 closed at one end and supported in spaced relationtherefrom by an angular baille 60 and opening into the resonator chamber 62 at the opposite end. One or more small brackets 64 support the tube 58 at the open end from the section 56. It will be noted that the louvers. 38 in the section 56 only open into the chamber 66 dened by the section 56 and the tube 58 throughout a portion of its longitudinal extent so that a neck or orifice is dened at 68 opening into the resonator chamber 62. Between they resonator chambers 28 and 62 is located a neck or orifice 10 similar in function to the orifice at 68. The orifices 68 and 10 may be varied as to diameter and length to alter the acoustic characteristics of the resonator chambers 28 and 62 which it will be noted are in compounding relation.

While it may be desirable in some cases to also A,

place the resonator chamber 30 in compounding relation with the chamber 62, in the illustrated embodiment a portion of the conduit 22-1s embraced by the chamber 30 and opens into the same through the louvers 38. I

Preferably the tortuous conduit defining the retroverted passageway for the exhaust gases is made up of a plurality of sheet metal sections welded together. After the separate straight through conduit sections 28, 22 and 55 have been assembled in the bailles 24 and 26 the return bend conduit sections 12 are telescoped with adjacent ends of the straight through conduit sections and welded or otherwise secured in position. As shown, the sections 12 are made up of complementary stamped halves 13 and 14 welded together along the iianges'16 and 11 to form an angular conduit for changing the direction of gas ow through 180 at opposite ends of the casing I0. y

Referring more particularly to Figs. l and '1'it will be noted that the louvers 38 are located in spaced groups along the conduit sections 20^and 22 and that the bailles 32 arev assembled upon these conduit sections in between the louver groups. As it is desirable that the baiiles 32 be threaded upon the conduit sections, after the louvers have been fabricated, it is necessary that the annular flange 18 defining the central opening in the baffle 32 be of greater inside diameter than the outside diameter of the conduit section in order to be threaded over the louvers. Accordingly, to assemble the baffles 32 in position upon the conduit section between the louver groups the opening 18 must be reduced in' some suitable manner in order to firmly secure the baflle 32 upon the conduit section. In Fig. '1 this has been accomplished by distorting the annular flange 18 by shrinking the same upon the conduit in a suitable die; the surplus material being deflected to define ears 80.

In Fig. 6 is shown a slight modification of the arrangement of the tortuous sections making up the conduit defining the passageway for the exhaust gases through the muffler. In lieu of having the parallel straight sections disposed in a single plane in an oval-shaped casing, with a cylindrical casing 82, the parallel straight conduit sections 84, 86 and 88 may be arranged at 120 apart and a tortuous conduit dened by connecting the straight through section through the employment of return bend sections 98 corresponding to the sections 12. The arrangement of the filter and resonator chambers shown in Fig. 1 may be likewise employed in connectionl with the arrangement of the straight through conduit sections shown in Fig. -6.

Heretofore in retroverted passage types of muillers it has been the practice for the straight through conduit sections to open directly into expansion chambers at opposite ends of the mufiier and to employ the expansion chambers for directing the exhaust gases along the return Aconduit or into'the conduit leading to the out-` let. With such a construction the exhaust gases in traveling from the inlet to the outlet do not have the well dened passage accomplished by the return bend conduit sections 12 disclosed in Fig. 1 and as a result there is greater lSStane of our muffler construction: As the flanges of the l angular conduit 12 are preferably welded to the casing I0 at |02 to support the same in position it is possible and may be desirable in some cases to omitl the baiiles 24 and 26 and Support the straighty through conduit sections within the casing entirely by the conduit 12. Such a construction would find application in cases where the compounding of the resonator chambers is not required and it is desired to open into a single chamber defined by the casing Il). rIt will also be readily seen that the entire internal structure of the mufller may be assembled outside the casing I0 and -then inserted and welded in position at |82 and |64. Preferably the sections 20, 22

.and 56 are only Welded in the assembly at one end to` permit the same to expand and contract in position. With reference to these sections, in practice they may be of different relative diameter and not of the same diameter as shown in Fig'. 1.

In lieu' of the louvers 38 opening into the chamber 30, a tube or opening may be stamped in and defined bythe stamped halves conducting the sections 12A and open into the -chamber 30.

The proportions of the acoustic wave attenuating structure of our muffler will, of course, vary in practice. Generally speaking, with'the acoustic range of the exhaust system determined by a wave frequency analyzer or in some other suitable manner, the chambers 36 are proportioned to attenuate the higher frequency wave ranges or bands andthe resonator chambers 28, 30 and 62 will be proportioned and tuned to attenuate the lower frequency ranges or bands. The compoundingI of the resonator chambers 28 and 62 materially increases the attenuatingV characteristics of the muilier and enables the capacity to be at a higher valuewith minimum chamber volume defined within the casing lll which 4accordingly enables compactness of construction.

Having thus described our invention what wev portions of said conduit, and means defining communication between said conduit and said structure.

`2..A muiller for 'internal combustion engines comprising an outer casing, a conduit made up of a plurality of sections collectively defining a retroverted passage for exhaust gases through said casing including inlet and outlet sections at the extremities thereof, spaced straight through sections disposedlongitudinally of the casing, angular sections for changing the direction of the gas iiow connecting `said spaced sections, said conduit being continuous throughout its entire length, acoustic wave attenuating structure em: bracing portions of said conduit. and means deiining communication between said con'dui said structure.

3. A muiiier for internal combustion engines comprising an outer casing, a conduit made up of and ^ a plurality of sections collectively defining a retroverted passage for exhaust gases through said casing including inlet and outlet'sections at the extremities thereof.' spaced straight through sections disposed longitudinally of the casing, angular sections for changing the direction of the gas ow, said conduit being continuous throughout its entire length and of substantially the same general cross-sectional area, acoustic wave attenuating structure embracing portions of said conduit, and means defining communication bei tween said conduit and said structure.

4. A muiiier for internal combustion. engines comprising an outer casing, headers at opposite ends of said casing, a conduit deiining a retroverted passage forI exhaust gases through said casing including inlet and outlet sections at the extremities thereofopening through said headers, said conduit being continuous throughout its entire length with the intermediate portion thereof deiining a tortuous path, spaced supporting structure disposed inwardly from said headers for supporting the tortuous portion of said conduit within said casing, acoustic wave attenuating structure embracing the intermediate 4portion oi' said conduit, and means deiining communication between said conduit and said structure. a

5. A muiiler for internal combustion engines comprising an outer-casing, a conduit deiining .a passage for exhaust gases through said casing i having an inlet andan Outlet, headers at opposite ends of said case through which said inlet and outlet extend,` a baille Within said casing spaced from said headers defining resonator chambers upon `opposite sides thereof, acoustic wave attenuating structure embracing one portion of said conduit, another portion ofsaid conduit opening into one of said resonator chambers,

and means deiining an opening between said chambers.

6. A muiiier for internal Acombustion engines comprising an outer casing, a conduit dening a passage for exhaust gases through said casing .having an inlet and an outlet opening through said casing, a baiiling means deiining a. resonator chamber within saidcasing, acoustic wave attenuating structure embracing a portion of said conduit within said casing and Without said chamber, said chamber being .disposed entirely to one side and longitudinally spaced from said structure, and means defining communication between said chamber and said conduit.

7. A muiiier for' internal combustion engines comprising an outer casing, means dening a passageway within said casing for conducting ex-' sage for exhaust gases through said casing,

haust gasestherethrough, lmeans dividing-said" casing into a plurality oi' resonator chambers,

acoustic wave attenuatingstructure embracing portions of said passageway, periorations in said, passageway along said portion opening into and communicating only with said structure, perforations in another portion of said passageway opening into one oi' said resonator chambers and means dening a communicating passage between i said resonators.

8. A muiiier for internal combustion enginescomprising an outer casing, headers located at ,opposite ends of'said casing, baiiiing members within said casing spaced from said headers and from each otherV to provide resonator chambers at opposite ends and centrally of said casing, a conduit having an inlet and an outlet opening through said headers Iand supported by said baffling member within said casing, said conduit extendingback and forth between said baille members with sections thereof between said baffies substantially straight and supported in spaced parallel relation, angular conduit sections for'reversing the direction of flow of exhaust gases through said parallel sections, said angular conduit sections being disposed within said resonatorfchambers located at opposite ends of said casing, acoustic iilter chambers embracing portions of said conduit between said baffling members, and means defining communication between said conduit and said iilter chambers and two or more oi' said resonator chambers.`

9. A muiiler for internal combustion engines comprising an outer casing, headers at opposite" ends of said casing, a supporting structure disposed Within and transversely of the longitudinal axis Vof said casing and spaced inwardly from said headers, a conduit defining a retroverted pastions of said conduit being disposed and spaced in substantially parallel relationship and being supported between said supporting structure, and angular conduit sections for directing the exhaust gas through 180 F. located upon opposite sides 4of said supporting structure and constituting 

